Distributed lighting systems typically have a central controller and have distributed/remote light fixtures connected to and controlled by the central controller, whereby the central controller receives power from a power source and receives control signals from one or more control inputs, and, in turn, provides power and control signals to the light fixtures. For example, multiple Light Emitting Diode (LED) light fixtures, which typically use a very small amount of electrical power as compared to “standard” light fixtures that use incandescent or fluorescent lamps, can be connected to central controller by low voltage wiring, which provides both power and control to the LED light fixtures.
While the power usage by LED light fixtures is substantially less than the power usage of standard light fixtures, there is still a need to address unnecessary power losses in distributed low voltage light systems. For example, in a standard type lighting system, a wall switch or the like will transmit electrical power to an associated light fixture when control circumstances are met. These could include, the wall switch is turned on by a user, or a dimmer switch is activated, or an occupancy sensor senses movement in a space, and so on. When the control circumstance is not met, electrical power to the connected light fixture is interrupted. However, in a distributed low voltage lighting system LED light fixtures are controlled by commands that have address data associated therewith such that when multiple light fixtures are attached to a single supply line, commands are acted on only by light fixtures that match the address of the transmitted data. In other words, many different light fixtures could function in many different ways based on the coded instructions sent to the light fixtures. A simple way to do this is with address matching where a command has an associated address and only light fixtures with that address will execute that particular command. This means that many different commands could be transmitted on a signal line (which can also function as the power transmission line to the connected light fixtures) but if none of the commands match addresses of the connected light fixtures, none of the connected light fixtures will execute any of the commands. So in effect, electrical power may be transmitted to multiple LED light fixtures, even when none of the connected LED light fixtures are being activated.
For distributed LED lighting systems this can lead to unnecessary power drain due to powering the LED light fixtures (or the associated equipment therewith) while not actually turning the LED light fixtures on. In the field of consumer electronics this function has been called standby power draw or “vampire current” referring to the way electronic current is consumed while the equipment is not in use. In fact, the Department of Energy has estimated that vampire devices accounts for 10% of energy used in an average home.
As stated previously, since standard lighting systems have traditionally worked by fully interrupting power to the attached light fixtures, the issue of standby power draw has not been a problem for known lighting systems. However, with the change to distributed low voltage lighting systems, this has become a problem for systems that combine both power distribution and lighting control signals onto a single output channel. As such, known distributed lighting systems do not adequately conserve power during periods of non-use.